1. Field of the Invention
The present invention relates to an optical writing controller, an image forming apparatus, and an optical writing control method.
2. Description of the Related Art
In recent years, computerization of information tends to be advanced, and image processing apparatuses such as printers and facsimile machines used for outputting computerized information and scanners used for computerization of documents have become essential equipment. Such an image processing apparatus is often a multifunction peripheral having an imaging function, an image forming function, a communication function, etc., and thus being capable of being used as a printer, a facsimile machine, a scanner, and a copier.
Among such image processing apparatuses, electrophotographic imaging forming apparatuses are widely used as image forming apparatuses used for outputting computerized documents. In an electrophotographic image forming apparatus, a photoconductor is exposed to form an electrostatic latent image, a developer such as toner is used to develop the electrostatic latent image and form a toner image, and the toner image is transferred onto a sheet of paper for output.
In such an electrophotographic image forming apparatus, a linear light source such as an LED array (LEDA) in which light emitting diode (LED) elements are arranged in a main-scanning direction may be used as a light source for exposing the photoconductor. In addition, a method of arranging multiple LED elements not only in the main-scanning direction but also in a sub-scanning direction so as to increase the exposure amount and the pixel density has been proposed (refer, for example, to Japanese Laid-open Patent Publication No. 2005-096112).
When multiple LED elements are also arranged in the sub-scanning direction, the respective LED elements arranged in the sub-scanning direction are sequentially lit with conveyance of the photoconductor surface so that the same position in the main-scanning direction of the photoconductor is exposed a plurality of times, and exposure energy can thus be increased. Thus, the light emitting elements are not limited to LED elements, and light emitting elements having a lower light quantity may be used.
An attachment error of the light emitting elements, however, may cause misalignment between the direction in which the multiple light emitting elements are arranged and the sub-scanning direction of the photoconductor drum. In such a case, the positions on the photoconductor exposed by the respective light emitting elements arranged to expose the same position in the main-scanning direction are gradually slightly changed, and the region on the photoconductor exposed by one row of light emitting elements becomes wider in the main-scanning direction. This results in uneven density in the formed image.
Such a problem of uneven density caused by the attachment error of the light emitting elements is not considered in Japanese Laid-open Patent Publication No. 2005-096112.
Therefore, there is a need to prevent deterioration in image quality due to attachment error of light emitting elements when a light source in which multiple light emitting elements are arranged in the sub-scanning direction is used for an optical writing device for forming an electrostatic latent image.